Engineering :: Heat Transfer

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211.

In a thermal power plant, cooling towers are used to cool

A.	steam	B.	condensed wate
C.	circulating	D.	All of the above

212.

In an air-conditioning plant a cooling tower is used to cool

A.	air	B.	refrigerant
C.	condenser water	D.	None of the above

213.

In a cooling tower which mode of heat transfer plays insignificant role?

A.	Evaporative cooling	B.	Convective cooling
C.	Radiaion	D.	All of the above

214.

A radiation shield should have

A.	low reflectivity	B.	high reflectivity
C.	high emissivity	D.	None of the above

215.

Two pieces of wood are placed in sunlight. One is painted white and the other is painted black. It can be concluded that

A.	White painted wood will not absorb any solar radiation	B.	Black painted wood will not absorb any solar radiation
C.	Black painted wood will absorb less heat as compared to white painted wood	D.	Black painted wood will absorb more hcat as compared to white painted wood

216.

A liquid to liquid counterflow heat exchanger is used to heat cold fluid from 50?C to 150?C. Assuming that the hot fluid enters at 250?C and leaves at 200?C, the log mean temperature difference for the heat exchanger will be closer to

A.	100?C	B.	128?C
C.	133?C	D.	137?C

217.

For a opaque body

A.	absorptivity = 0	B.	reflectivity = 0
C.	absorptivity = reflectivity = 1	D.	absorptivity + reflectivity = 1

218.

In case of white body, absorptivity is

A.	Zero	B.	Between 0 to 0.5
C.	More than 0.5	D.	1

219.

In case of a body transparent to thermal radiation

A.	absorptivity = 1	B.	reflectivity = 1
C.	absorptivity = reflectivity = 0	D.	transmissibility = 0

220.

Any of the following could be the unit for Stefan Boltzmann constant EXCEPT :

A.	W / m2k4	B.	erg / cm-k4
C.	cal / cm2-sec-k4	D.	BTU/ft2-hr-R4